This application claims the priority of German Patent Application No. 197 15 880.3-53, filed Apr. 16, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a system composed of wire-bus linked control devices having a reduced system bias current requirement.
Many technical products and systems are being revolutionized by the use of bus systems. One example is the CAN bus in a vehicle or other transport means, such as in "CAN-An Auto Bus" in FZ Messen und Prufen, June 1992, pp. 46-53, in which a plurality of electronic control devices are connected together by a two-wire data bus. The functional transfer on the data bus that is thus made possible saves on wiring costs and permits a simple and readily expandable system architecture.
Such linked systems composed of wire-bus linked control devices have the functional disadvantage that the data bus as a rule is activated only by activating a central current flow gate, such as the "ignition switch" in a vehicle for example. This means first of all that either control devices must be supplied with input signals in conventional fashion, despite the presence of a data bus in order to be able to operate with the corresponding functions when the system is shut down, for example when "Terminal 15" is not energized in a motor vehicle, which in turn results in a disadvantageous requirement for many conventional leads. (One example of this is the prompting of a group of instruments in the dashboard by a door contact in order to present display information on the instruments.) On the other hand, while the transmission of the hazard warning function of a vehicle over the CAN bus for example is theoretically possible, when "Terminal 15" is not energized, it is impossible to display the hazard warning system in an energized state when the instrument panel is not energized. In a motor vehicle for example this also means that control devices can provide or permit a continuous standby operating state with the CAN bus activated. However, this results in a high bias current requirement for the entire system, which adversely affects the energy balance of the electrical system.
IBM Technical Disclosure Bulletin, Vol. 25, No. 7B, 12/1982 describes a computer system based on intelligent macros, whose components are distributed along a bus and which has a reduced current requirement. In this arrangement, macros are used to selectively apply required current to the specific components necessary for performing specific operations in the computer system. However, this assumes that each of the functions that can be addressed by macros performs a specific macro discrimination function that would not be possible without bias current supply.
The object of the invention is to provide a system which is composed of control devices that are linked by a wire bus, and which has a reduced total bias current requirement. In other words it is not connected to bus operation when the system is not in use.
This and other objects and advantages are achieved by the system of wire-bus linked control devices according to the invention, in which all of the control devices are connected to two bus bars for their operational power supply and the bus bars are permanently connected with the supply poles of an operating current source. One of the control devices is equipped with a standby operating function with prompting readiness and is constantly active in prompting readiness; apart from its communications link with the bus, this control device has at least one separate signal input through which it can be prompted. In addition, it has a control output which (from prompting readiness) is able to output a connect signal when its normal operating state is reached. Each of the other control devices has internal means for its controllable power supply from the two bus bars and a connect control input for receiving a control signal to activate the internal means. All of these control inputs are connected with the above-mentioned control output of the standby-capable control device, so that when the connect signal is output, the other control devices can be energized and thus placed in operational readiness.
This system configuration results in a very low bias current requirement, since only a single control device needs to be designed for a standby mode with prompting readiness. When an energy storage device is used as the operating power source, for example, a theoretical service life of at least 200 days with a 10 Ah drop in capacity is guaranteed with 1-2 mA total bias current. Since the self-discharge rate of the energy storage device (a lead storage battery for example) can be considerably greater than 50 mAh/d, self-contained or mobile systems according to the invention are possible in which the bias current consumption is of no further practical significance.
In one embodiment, the system is part of a vehicle. Such a system has the advantage that hazard warning information, for example, can be transmitted over the data bus. According to another feature of the invention, a signal produced by the actuation of a door contact can be supplied to the control device with a standby operating function at its (at least one) separate signal input so that, for example, the group of instruments in the instrument panel of a motor vehicle can be prompted via the data bus.
In another embodiment, the control device with a standby operating function has at least one separate signal input for receiving a signal produced by the reception in the vehicle of remote control information received from the outside.
According to another feature of the invention, the control device with the standby operating function can be equipped to recognize entry into the transport means. According to still another feature of the invention, one of the other control devices can integrally contain at least functions for monitoring and controlling driving authorization and be so designed that it is able to transmit information received and labeled "transport means start" to the drive components of the transport means and thus can trigger the start of its driving unit.
In another embodiment, the control device with the standby operating function can integrally combine the function of a control device for monitoring and controlling driving authorization, and is designed so that it can transmit an item of information labeled "transport medium start" to the drive components of the transport means and trigger the starting of its drive unit as a result.
According to another feature of the invention, the bus is a CAN-based type. Finally, the subject discussed in one of the other control devices is one of the following: an instrument cluster in the dashboard, an ABS control device, an engine control device, or a comfort control device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.